Riboflavin, also known as vitamin B.sub.2, vitamin G and lactoflavin, has physiological significance in the metabolism of protein, fat and nucleic acids. Because it is considered to be an essential B vitamin, riboflavin is added to poultry and livestock feeds to supplement naturally occurring levels. Total worldwide demand for riboflavin supplements is approximately 1.4 million kilograms.
Finished animal feeds are commonly produced through the mixing of concentrated premixes with the bulk of the feed. Premixes are a blend of the pure vitamin or nutrient with a suitable carrier. Mixing the premix with the bulk of the feed assures homogeneity or even distribution of the vitamin in the finished feedstock. If pure vitamin rather than a premix is added directly to the bulk of the feed, there is a greater likelihood of uneven distribution. Further, if the pure vitamin retains electrostatic charge, or has poor flowability or dispersability and/or is hygroscopic, its addition to bulk feed is even more likely to result in uneven distribution. For these reasons, the concentrated vitamin is not normally added directly to the bulk feed.
Products having a riboflavin concentration above 90% by weight typically have a low bulk density, develop electrostatic charge, have a smaller particle size and poor flowability and are hygroscopic. The tendency of particles to develop or retain electrostatic charge can cause adherence of the particles to the surfaces of weighing, transportation, mixing and storage devices. Electrostatic charge tends to increase with smaller particle size. It has been reported that the electrostatic charge of high purity riboflavin is due to the threadlike riboflavin crystals which tend to have polar ends. Hygroscopicity refers to the tendency of a substance to absorb moisture from the environment. Because of its hygroscopic nature, high purity riboflavin must be stored in a low-moisture environment. Flowability refers to the ease with which a substance flows in a smooth and uninterrupted fashion. Flowability generally increases with bulk density and is adversely affected by electrostatic charge and hygroscopicity.
To produce homogeneous distribution of a vitamin in a finished feedstock, feed manufacturers seek premixes having the following properties: vitamin stability, good flowability, minimal electrostatic effects, and minimal hygroscopicity. To conserve shipping costs which are based on both volume and weight and to minimize storage cost and facilitate handling, feed manufacturers seek premixes having a smaller volume made possible by high potency and high bulk density.
Efforts have been made in the past to produce a riboflavin product having minimal electrostatic charge, high potency, high bulk density, improved flowability and minimal hygroscopicity. In Cannalonga et al., U.S. Pat. No. 3,959,472 (1976), oyster shell flour and maltrin are added to produce a riboflavin product reported to be free-flowing, non-dusting and static free. The product is described as comprising 45-65% riboflavin with a bulk density of 35-36 pounds per cubic foot (lbs/ft.sup.3). The composition is produced by spray drying an emulsion to produce a final product having by weight 45-65% riboflavin; 15-25% oyster shell flour; 15-35% maltrin; and 1-5% silicic acid.
Other riboflavin products known to exist in the market contain other carriers which may serve to reduce electrostatic charge, increase bulk density and improve flowability. "MICROVIT RIBO".TM. feed supplement produced by Rhone Poulenc contains soy flour and oil and dry fermentation solubles. "ROVIMIX B2 80 SD".TM. feed supplement manufactured by Hoffmann LaRoche contains 20% by weight skim milk.
As described above, riboflavin products having a purity greater than 90% by weight typically are hygroscopic and have electrostatic properties that are detrimental to flowability. Products having lower riboflavin concentrations have lower potencies which in turn can mean greater shipping and storage costs. Thus there is a need for a riboflavin containing material having a higher bulk density and a greater potency to minimize volume and shipping costs while having minimal electrostatic charge and hygrocopicity to enhance flowability. It would be particularly advantageous if the above physical characteristics could be produced by the addition to substantially pure riboflavin of a carrier having a low cost.
It has now been found that the composition of the present invention fulfills these needs by using a carrier which is also inexpensive and readily available.